The invention relates generally to the field of telecommunications, and more specifically to the field of mobile communications, e.g., cellular telephones.
U.S. Pat. No. 5,295,180 describes a system to generate zone identification signals for mobile communication systems. Terminals know zone identity by analyzing a signal emitted by a mark transmitter. This system includes the possibility in which, in case of zone overlapping, one of the mark transmitters has a higher priority, and can interfere with the signal of the others. In other words, the system uses interfering signals to define influence areas of mark transmitters.
However, the purpose of this system is not the disabling of terminals present in a given zone, and it does not take into account propagation properties in closed spaces, in order to generate interfering signals. Because of these reasons, it cannot be used to disable calls in closed spaces, neither in an indiscriminate nor in a selective way.
In the military, and for electronic war applications, there are devices that detect and jam enemy systems, such as radar or communications. Also in the military context, there are indiscriminate interference generators to disable devices that activate bombs remotely.
The disabler for mobile communications devices (e.g., cellular telephones) is a device to be placed in an enclosed area, whose functionality consists of: (a) detecting the existence of carrier signals from any mobile communications base station containing signaling channels; (b) measuring the carrier signal level; and (c) generating noise signals to affect these signaling channels. When the noise signals mask or xe2x80x9cjamxe2x80x9d the detected carriers, no mobile terminal/telephone present in the enclosed area will be able to receive the signaling information from the base station that generated it. As a consequence, incoming call alarms directed to the user of the mobile terminal/telephone are blocked.
Therefore, the main advantage of this system is that mobile terminal activity is disabled, independently of whether the user has it turned on or off, in enclosed areas in which incoming call alarms are a nuisance or where terminal activity may cause trouble. The disabler is tuned in such a manner that its interference signals will not have an effect outside the enclosed area where the device is installed.